Nowadays there are different ways to restore absent teeth, consisting of removable or fixed prosthetic solutions, according to the possibility of each case. Natural teeth can be restored through total or partial removable prosthesis or unitary or multiple fixed prosthesis above natural teeth or implants. The dental implant is a device that simulates a dental root and it has the objective of restoring the dental crown through an abutment—also known as pillar or connector—which is connected to an osseointegrated dental implant and supports the prosthetic crown which will assume the aesthetics and function of a tooth.
The connection of the abutment to the implant is usually made by screwing or through a system of frictional fitting known as Morse taper, the later showing better sealing results between the implant and the abutment, besides having self-fixation properties as the masticatory force contributes to the better interlock of the parts. One way of connection is carried out by screwing through a central portion in the abutment, which receives a proper screw threaded inside the implant. This method of fixation is still very much used, although it presents problems of fatigue fixing, which promotes loosening of the screw, necessitating maintenance of the prosthesis.
In the phases of implant installation, there are some previous treatments/maneuvers to be executed on the receiving bone bed. Firstly, the space readiness and quality of the receiving place of the implant is checked and if necessary, the use of bone grafts to make the implant installation possible can be considered. This phase of installation of implants is identical for all of the types of dental prosthesis and the technique, as well as the processes, is well known now.
The bone tissue receives hole operations with special drills specifically gaged for adaptation of the chosen implant, considering its height and diameter. Still in this surgical act, the implant is threaded to the bone through a specific key until reaching the appropriate insert level, when then the implant receives a coupled or screwed cover right before the gum tissue is sutured, covering the implant completely. Starting from this moment, the inertia of the system promotes the phenomenon known as osseointegration that consists of the formation of a stable and functional union between the bone and the surface of the implant, what usually happens in a period from 3 to 6 months.
Once the implant is osseointegrated, the beginning of the prosthetic sequence is given. Surgical access to the implant is done through a small gum incision, and then the protecting cover of the implant is removed and replaced by a healing abutment, which remains in the place for about 2 weeks and has the objective of shaping the gum for subsequent adaptation of a prosthetic abutment. This abutment consists of the link that joins the dental crown to the implant, in other words, it is the communication between the tooth and the artificial root.
A diversity of abutments exists with different indications that vary according to the case, respecting factors such as the prosthesis type (fixed or removable) that is wanted, how many implants that will be used in the prosthesis (isolated or multiple elements), area of the tooth to be replaced (anterior or posterior), if the abutment will have to be customized, character of the prosthesis (temporary or definitive), gingival morphology (thick or thin) and if it is necessary to compensate some inclination of the implant, etc.
Among the existing problems found in the installation of implants, we can mention the lack of enough bone and with good enough quality in the area to receive the implant. Another limiting situation is the morphology of the existing bone itself. There are some ways to overpass the mentioned issues by using bone graft, shorter implants or, most commonly, placing implants in an angled way in order to find adequate bone support. That will make it necessary to use angled abutments, that is, abutments connecting to the implant that are angled to compensate the non-ideal implant axis.
The presence of acquired or congenital bone deformities should be considered in the preparatory surgeries in order to reestablish the anatomy and the morphology of the bone and, consequently, of the gum tissue that recovers it, aiming for the best aesthetic result in the adaptation of the prosthesis.
In general, in order to allow several adaptations of the prosthesis according to the biomechanical needs of each patient, angled prosthetic abutments with predefined angles are used, the angles ranging from 0° and 25° or 30°, which are molded or machined.
Although quite useful and sometimes indispensable, existing angled abutments have some limitations, the main one being the fact that they cannot provide intermediate or customized inclinations and also the fact that most manufacturers offer only one or two alternative angulations. This limitation makes it difficult for the professional to achieve perfect compensation in angles for all cases, since the desired compensation may not be the one offered by the market.
Another drawback of those pre-angled abutments is related to the need of inventories in the clinic to assist the diversity of clinical cases, otherwise the professional will be subject to one period of delivery of the special components.
Among other existing concepts to facilitate angled abutments are included the embedded, machined or molded components such as those shown in the patent documents PI9604737-2 and WO2010150188. In these cases when there is the need for assembling the components, it is obvious that the more components to the same physical space, the less space is available for walls and heights to dispose each part of the set, showing the possible structural weaknesses of those systems.
We can also mention the patent document US2011275030 that introduces a slopping abutment of single body and Morse taper that solves several problems as compared to the previous state of the art. Said document presents a schematic view partly in section of an area of the jaw containing angled abutments (see FIG. 6), where one can observe the method of positioning of the abutments for aesthetic alignment.
Despite the constant evolution, in all of the cases above it can be observed that the prior art only presents abutments built with preconceived angles, as in the case of patent US2011275030 typically in groups of 10, 15, 20, and 30 degrees, and not from degree to degree, for instance, creating mismatches and forcing the professional to acquire a stock of components to suit each clinical case, or then await order periods for each specific component used in each customer as these are products of high precise construction.
An alternative for determining the appropriate angle is disclosed in patent document U.S. Pat. No. 4,758,161, which introduces a thermoplastic coping insert for shaping models to be used to achieve definitive prosthetic abutments.
Referred coping insert comprises a lower portion that fits into an opening in an osseointegrated implant; an abutment head joined to the top surface of the dental implant; a bendable restriction or groove to facilitate bending of the insert at the restriction when the insert is heated to the softening temperature of a thermoplastic for determining the angle according to the biomechanical needs of each patient, such angle being determined at the mouth, that is, at the site of the implant; and a mounting area atop the restriction for receiving and supporting a dental prosthesis.
Initially, the insert is heated in order to be molded to the proper inclination, and then it is positioned in the mouth and later removed and used as a temporary template to shape a model for achieving a definitive prosthetic abutment.
Thus, the professional achieves the definitive prosthetic abutment with the ideal inclination for each patient, the definitive prosthetic abutment being shaped by any convenient material such as gold.
Another alternative to angular orientation of the prosthesis is disclosed in the patent document U.S. Pat. No. 4,645,453, which reveals a bendable adapter provided with a means of connecting to an implant positioned in the gum tissue; an intermediate narrow portion that is necked down to provide a flexible region close to the gum tissue; and, at the upper end, a mounting and fastening area for a prosthesis. Thus the projecting part of the bendable adapter may take various forms to maximize aesthetic requirements of the patients.
Disadvantageously, this patent document presents an intermediate narrow portion that is necked down to provide a flexible region close to the gum tissue, as shown in FIG. 1, reference 26, comprised of two sections at an angle converging on a straight section, which may cause cracks in the regions of convergence between the compressed angled and straight sections. These cracks may cause fatigue cracking with a few charging cycles.
Moreover, both alternatives disclosing prosthetic abutments provided with narrow regions for angular orientation do not define a customized bending method for definitive prosthetic abutments to help dental surgeons and/or prosthetic technologists to determine an inclination angle to each patient, in an individualized and accurate manner, without compromising the dimensional and mechanical properties of the abutment.